Cane toads, armadillos on the march

Is global warming the reason why two tropical animal species, cane toads and armadillos, are migrating to cooler zones in Australia and America? Millions of poisonous cane toads, originally found only in Central and South America, are moving south in Australia, while large numbers of armadillos, once found only in South America, have worked their way northward through the United States, and may even invade Canada before long.

Cane toads are large, heavily built amphibians with dry, warty skins. Adults toads are four to six inches (10-15 cm) long, but they can grow up to 9 inches (23 cm) or more. They're as dangerous as they're ugly. Their eggs, tadpoles, toadlets and the adult toads are all toxic. If the animals feel threatened, or are handled roughly, they squirt poison from glands on their shoulders. Their venom causes rapid heartbeat, excessive salivation, convulsions and paralysis, and has killed many native animals and family pets.

"They were deliberately introduced from Hawaii to Australia in 1935, to control scarab beetles that were pests of sugar cane," says The Australian Museum website. [The experiment failed.] "In 2002, cane toads occur throughout the eastern and northern half of Queensland and have extended their range to the river catchments surrounding Kakadu National Park in the Northern Territory. In New South Wales they occur on the coast as far south as Yamba, and there is an isolated colony near Port Macquarie."

They've marched even further south since that was written. They pose a huge problem, as females lay 8,000 to 35,000 eggs at a time and usually breed twice a year.

In the US, armadillos are also known as Texas speed lumps, possums on the half shell, and Hoover hogs.

First found in southern Texas, near the Mexican border, they have made their way as far north as Illinois. An Illinois Natural History Survey has recorded 80 sightings in recent years, mostly in the southwestern corner of the state.

"Armadillos have been marching north and east on their clawed feet since first being documented in the Rio Grande Valley of southern Texas in 1849," Chicago Tribune staff reporter Ted Gregory wrote on March 18, 2005. "That migration has been aided in large part by the transformation of forests to farm fields and yards, which drove out armadillo predators and created near ideal foraging conditions for the hard-shelled mammals.

"By the 1970s, armadillos were digging up and munching on beetles, termites and caterpillars and nibbling on carrion in Mississippi, Georgia, Alabama, Colorado, Kansas and Tennessee. The mammals' territory expanded in those states and moved into southern South Carolina by 1995, when some had been spotted as far north as Nebraska."

A University of Illinois website says:

A newcomer to the southern part of our state seems to be stirring up more curiosity than eradication plans--the nine-banded armadillo.

Nine-banded armadillos are the most numerous and widely distributed of the twenty species of armadillos that exist today, and the only kind that inhabit the United States. They are native to South and Central America, but they've been expanding their range for at least the past hundred and fifty years...

Will Illinois be added to the list of states that armadillos call home? People have reported seeing them here since the 1970s... How armadillos arrive in Illinois is an open question. They might be brought by people and released, as they were in Florida. Or they might come as stowaways in cargo on barges, trains, or trucks. Or they might arrive on their own power walking across bridges, or--unlikely though it may be--even somehow crossing the Mississippi river.

Although we know that armadillos can get to Illinois, we don't yet know whether or how well they might become established here. Cold will eventually stop their spread north, since they can't hibernate and depend for food on insects and other creatures they find by digging in the earth. Where the ground stays frozen for too many days in a row during winter they are unable to dig for food and can't survive. The current prediction for their northern limit is a line that runs across the state about a third of the way up from the bottom.

Whether or not armadillos become Illinois residents, they are fascinating for their many quirks.

When they are startled, armadillos may jump four feet into the air, and they are surprisingly fast for such ungainly looking creatures.

Armadillos don't float naturally, so they cross small bodies of water by walking across the bottom, like divers wearing weights. When they must swim, they can make themselves buoyant by gulping air to partially inflate their intestines.

Armadillos typically give birth to identical quadruplets every year, and they can delay pregnancy at the earliest stages to ensure that young will not be born until weather conditions are favorable.

And of course, armadillos are the only North American mammals that grow their own armor.

A news item in the Dallas Morning News says "Some think armadillos will eventually spread along the East Coast as far north as Massachusetts' Cape Cod and, if introduced into California, could range north into British Columbia, Canada."

Armadillos often star in TV nature shows. An amorous pair amused or shocked viewers of the Late Night with David Letterman show a few weeks ago. If you want to be amused, click on the last item in the links list below. If you don't choose to be shocked, just ignore it.